docs: add a real live-update demo GIF to the README

Driven end-to-end through the actual server + live-reload path (real
2s-poll cycles, real page reloads, a real click on the theme toggle) —
not faked frames. Fictional task, no real work or data. Sped up in the
README with a caption saying so.

README.md

@@ -24,8 +24,9 @@ report of its own work — status, reasoning, screenshots, a running log — and
 you watch it update in a browser tab in real time, with zero setup.
 
 <p align="center">
-  <img src="docs/screenshots/report-light.png" alt="A sitrep-panel report showing a status board, a running narrative, a screenshot, and a newest-first log for a fictional 'add rate limiting' task">
+  <img src="docs/screenshots/demo.gif" width="640" alt="sitrep-panel updating live in a browser tab: the board, current-work narrative, a screenshot, and the log all filling in as a fictional task progresses, then a dark-mode toggle">
 </p>
+<p align="center"><sub>Sped up. The real cadence is a poll every 2 seconds — this is a fictional demo task, not real work.</sub></p>
 
 ## Why it's different